1. Field of the Invention
The present invention relates to a control system for sewing machines, and more particularly to a technique to simplify the setting of values for various parametrical items on the material-feeding and sewing operations depending on a kind of a material to be sewn, e.g., a sweat shirt and a T-shirt.
2. Description of Related Art
An embroidery sewing machine is provided with an embroidering unit or device to drive and move an embroidering frame to which a material (i.e., a sweat shirt, a T-shirt or the like) is set. Prior to the sewing operation, the embroidering frame that is conformed in size and configuration to a pattern to be embroidered is attached to the embroidering device. A desired embroidery pattern is selected, and to form the selected embroidery pattern by stitches an operator sets various parametrical items on the material-feeding and sewing operations in terms of setting values while viewing its related display on a monitor screen. Examples of those parametrical items are "sewing speed", "sewable area" within the embroidering frame, "stand-by position" of the embroidering frame, "thread-breakage sensitivity", and "number of stitch-back stitches" for the thread breakage.
A value to be set for the parametrical item "sewing speed" is the number of stitches formed per minute. A value to be set for the parametrical item "sewable area" is positional data indicative of two points (i.e., the left upper point and the right lower point) that designate within the embroidering frame an area (a sewable area) where an embroidery pattern can be sufficiently formed by stitches. A value to be set for the parametrical item "stand-by position" is positional data indicative of a position (a stand-by position) to which the embroidering frame is retracted so that the sewed material can be easily removed from the embroidering frame after the sewing operation is complete. A value to be set for the parametrical item "thread-breakage sensitivity" is the number of stitches for a thread-breakage sensitivity to determine whether or not a thread breakage sensed by a sensor is reliable. A value to be set for the parametrical item "number of stitch-back stitches" is the number of stitches by which a needle is to be returned corresponding to the number of idle stitches subsequent to the thread breakage.
Those parametrical values are set according to a kind of a material to be sewn or the size of an embroidery pattern. The "sewing speed", "thread-breakage sensitivity" and "number of stitch-back stitches" are set in terms of corresponding numerical values. The "sewable area" and the "stand-by position" are set using a "cursor" or a "marker" on the screen of the display device or monitor.
As described above, to embroider the material with the embroidery sewing machine, preparatory work is required. That is, every time the material is embroidered, the material, (e.g., a sweat shirt or a T-shirt) is set to the embroidering frame, a desired embroidery pattern is selected, and optimal values are set for the plurality of the parametrical items in accordance with a kind of the material and the size of the embroidery pattern. Therefore, when the material is changed, for example, from a sweat shirt to a T-shirt or vice versa, a machine operator sets again the optimal values for the parametrical items anew. In a case where the material is frequently changed, this complicated value setting work is troublesome and lowers the working efficiency.